<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8" />
  <title>Hello World</title>
  <script src="https://unpkg.com/react@16/umd/react.development.js"></script>
  <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
  <script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
  <style>
    html,body,#root{
      width: 100%;
      height:100%;
      margin: 0;
      padding: 0;
    }

    .SplitPane{
      width:100%;
      height:100%;
    }

    .SplitPane-left{
      float:left;
      width:30%;
      height:100%;
    }

    .SplitPane-right{
      float:left;
      width:70%;
      height:100%;
    }

    .Contacts{
      width:100%;
      height:100%;
      background:lightblue;
    }

    .Chat{
      width:100%;
      height:100%;
      background:pink;
    }
  </style>
</head>

<body>
  <div id="root"></div>
  <script type="text/babel">

    function Contacts(){
      return <div className="Contacts"/>;
    }

    function Chat(){
      return <div className="Chat"/>;
    }

    function SplitPane(props){
      return (
        <div className="SplitPane">
          <div className="SplitPane-left">
            {props.left}
          </div>
          <div className="SplitPane-right">
            {props.right}
          </div>
        </div>
      );
    }

    function App(){
      return (
        <SplitPane left={<Contacts/>} right={<Chat/>}/>
      );
    }

    ReactDOM.render(<App/>,document.getElementById('root'));
  </script>
  <!--
      Note: this page is a great way to try React but it's not suitable for production.
      It slowly compiles JSX with Babel in the browser and uses a large development build of React.

      To set up a production-ready React build environment, follow these instructions:
      * https://reactjs.org/docs/add-react-to-a-new-app.html
      * https://reactjs.org/docs/add-react-to-an-existing-app.html

      You can also use React without JSX, in which case you can remove Babel:
      * https://reactjs.org/docs/react-without-jsx.html
      * https://reactjs.org/docs/cdn-links.html
    -->
</body>

</html>